A wide variety of modern medical testing instruments utilize leads to either sense electromagnetic energy or to deliver electromagnetic energy for testing or for therapeutic reasons.
A variety of different medical testing regimens utilize test leads for sensing or receiving electromagnetic energy emanating from the human body. For example, electrocardiogram testing (EKG or ECG) senses electrical impulses associated with the beating of the heart. Electroencephalogram testing (EEG) senses electrical activity related to brain function. Electromyelogram testing (EMG) senses electrical activity related to the functioning of skeletal muscle.
These instruments often are utilized to sense extremely low power levels emanating from the living organisms such as the human body. Because of the low energy levels involved, small variations in the electrical characteristics of the electrical leads can create significant differences in results.
In general, the leads used with these instruments are used for tests that are acute in nature. That is, the leads are applied to the test subject for a relatively short period of time. The leads are not intended for long-term use. An example of long-term use would be the leads that are implanted with an implantable cardioverter/defibrillator or pacemaker. The leads involved there are required to be more robust than the leads in question here. In addition, since those leads are associated with expensive devices and surgical procedures and lead expense is relatively trivial in the scope of the entire operation cost is not a great concern.
Therefore, lead sets utilized with these acute testing and treatment instruments are often disposable in nature. They are intended for use only once and are then intended to be discarded. Because of this disposable nature the market for leads for acute use is more price sensitive than that for chronic leads. Nonetheless it is essential for accurate diagnosis and treatment that acute use leads be within the desired range of electrical parameter tolerances.
In addition, some medical testing instrumentation senses electromagnetic radiation in the ultraviolet, visible light or infrared wavelengths. For example, certain intracardiac catheters contain fiber optic leads that sense reflected light radiation from structures in the heart. In this application, the applicant will primarily refer to leads. It should be understood that for the purposes of this application the term ‘lead’ also includes fiber optic strands. The invention is equally applicable to leads using fiber optic strands to transmit light energy.
Because sensing leads may be used to detect extremely low power levels, minor damage or deterioration may create significant loss of sensitivity and thus alteration of testing results. Handling the leads more than necessary may accelerate damage to them.
Various leads are used in medical testing to stimulate biological activity. For example, certain types of cardiac testing provide stimulation to the heart in addition to sensing EKG activity. An example of such testing is disclosed in U.S. Pat. No. 6,129,678 to Ryan and Hoium. This application is incorporated herein in its entirety by this reference.
Lead sets can also be used to deliver electromagnetic energy for therapeutic reasons. For example, intracardiac catheters often are utilized to deliver energy for purposes of ablating tissue. Such electromagnetic energy may be delivered, for example, in the form of radio frequency energy or laser light energy.
Often, multi-purpose lead sets may be utilized. Multi-purpose lead sets may contain electrical leads for sensing, electrical leads for stimulating, electrical leads for therapeutic purposes, fiber optic leads for sensing or therapeutic purposes, or any combination thereof.
With the proliferation of leads used for medical testing purposes, a variety of problems arise. First, any type of lead set will suffer degradation of performance with use. In use, leads may be exposed to variations in temperature, bodily fluids, skin oils, atmospheric oxygen and high oxygen environments. Any of these factors will tend to lead to corrosion of metal parts of the lead as well as loss of the lead's insulator dielectric strength. For example, skin surface leads have primary attributes of impedance, inductance and capacitance. Over time, and with exposure to environmental factors, these qualities of skin surface leads can change. If these qualities change sufficiently, electrical impulses transmitted by use of the skin surface leads are altered. Thus, the data measured will be changed causing instrument readings to be imprecise, potentially leading to an erroneous diagnosis.
Additionally, certain types of medical testing leads may suffer degradation of their electrical or optical qualities over a period of storage. Again, corrosion, loss of dielectric strength or other deterioration may affect the electrical qualities of leads while in storage.
The proliferation of leads also creates a variety of potential problems created by the use of the wrong leads for a given circumstance. Multipurpose instrumentation may require different types of leads for different testing or treatment scenarios.
Lead sets may be very similar in appearance and, if reusable, once removed from their packaging may be difficult to identify. The use of the wrong set of leads for a given testing procedure may lead to degraded or altered data results and potentially erroneous diagnosis. In addition, leads used for stimulation or therapeutic purposes may not deliver the appropriate level of stimulating or therapeutic electromagnetic energy. This can result in over treatment or under treatment of the medical condition in question.
Under some circumstances there may be a need to perform medical testing when the desired lead set is unavailable. Under these circumstances it would be desirable to be able to determine whether an alternative lead set would provide acceptable results. In some circumstances instrumentation may be calibrated to a particular lead set to increase the precision of the result.
Many types of lead sets are provided in disposable configurations intended for a single use and then immediately discarded. With the increasing pressure to hold down costs there can be a temptation to reuse lead sets that are intended for only a single use. This activity increases the risk of erroneous diagnosis and also potentially increases the risk of infection if the lead set is intended to be sterile at its initial use. It would be desirable to be able to determine whether a lead set had previously been used and to prevent the reuse of lead sets that are intended for a single disposable use.
Thus, it would be desirable in the field of medical testing arts to be able to readily test leads prior to use, even prior to opening the packaging, to determine whether those leads have deteriorated in storage, to ascertain that they are the appropriate leads for the test or that they are an acceptable alternative set. In addition, it would be desirable to determine whether reusable leads have degraded from the rigors of use prior to their application. It would be further desirable to identify and/or disable reuse of single use leads so that they could not be reused beyond their desired intent.